Method, device and system for performing nav control on node and node

ABSTRACT

The present invention discloses a method, a device and a system for performing NAV control on a node and a node. The method includes: updating a local NAV value to a preset first value when it is determined that a preset first field of a monitored MAC frame carries a first identity, wherein the first value is smaller than a current local NAV value and the MAC frame of which the preset first field carriers the first identity is transmitted by a TXOP responder after receiving a last MAC frame transmitted by a TXOP holder. The method, device, system and node may enable a hidden station to enter a channel access competition state timely, thereby solving a problem of regional discrimination of a station.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/196,568, filed on Mar. 4, 2014, which is a continuation ofInternational Application No. PCT/CN2012/081493, filed on Sep. 17, 2012,which claims priority to Chinese Patent Application No. 201110273817.2,filed on Sep. 15, 2011. The afore-mentioned patent applications arehereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present invention relates to a field of communication, in particularto a method, a device and a system for performing NAV control on a nodeand a node.

BACKGROUND

A basic component of a wireless local area network (WLAN) based on anIEEE 802.11 technology is a basic service set (BSS), which consists ofstations (STAs) with certain association in a certain area of specificcoverage, such as a second basic service set (BSS2) and a third basicservice set (BSS3) shown in FIG. 1. In a BSS network, a central stationfor specially managing the BSS is named as an access point (AP), andother stations (STAs) in the network are associated with the AP. Anextended service set (ESS) may be formed by connecting multiple BSSnetworks with each other through a distribution system (DS). Inaddition, in the absence of the AP, the stations (STAB) may organize anetwork by themselves to directly communicate with each other, and thisnetwork is an independent basis service set (IBSS), such as a firstbasic service set (BSS1) shown in FIG. 1. In embodiments of the presentinvention, the access point (AP) and the station (STA) are collectivelynamed as nodes.

Distribution nature of channel access of the WLAN based on the IEEE802.11 technology brings that a carrier monitoring mechanism is crucialfor a collision-free operation. A physical carrier monitoring mechanismlogically existing in a PHY layer takes charge of detecting transmissionof other nodes. However, due to a reason such as a geographic position,physical carrier monitoring may not detect transmission of all thenodes, namely a hidden node problem exists. For example, as shown inFIG. 2, a data transmission path is established between a first station(STA 1) and an access point (AP), and a signal transmitted from thefirst station (STA 1) may be detected by the access point (AP) and asecond station (STA 2), but for a remote node, a third station (STA 3),only a signal transmitted from the access point (AP) may be detected anda signal of the first station (STA 1) may not be detected. When thefirst station (STA 1) transmits a signal to the access point (AP), thethird station (STA 3) may still think that a channel is in an idlestate, thereby causing interference to receiving the signal of the firststation (STA 1) by the access point (AP).

A network allocation vector (NAV) is a mechanism which may be used forovercoming the above-mentioned hidden node problem. A function of NAV islocated on a MAC layer, and provides a virtual carrier monitoringmechanism to enhance physical carrier monitoring. The mechanism ismainly realized by setting a NAV value in each node. Specifically, whena certain node A transmits a MAC frame to a certain target node, NAVvalues of all stations (except a target station successfullydemodulating the MAC frame) under the coverage of the node A are updatedaccording to a time length field borne in a frame header of the MACframe. The time length field includes a time value using a microsecond(us) as a unit, and the value may be a continuous time length from theend of the last physical layer convergence procedure (PLCP) protocoldata unit (PPDU, PLCP protocol data unit) bearing the MAC frame, inwhich channel resources are in an occupied state.

In 802.11e, another important concept, namely a transmit opportunity(TXOP) is introduced, which means a bounded time period in which a nodemay transmit a specific communication category and may be acquiredthrough a competition mechanism of a competition period. Within a TXOPtime limit, a certain node exclusively occupies a channel resource andmay continuously transmit a data frame, a control frame and a managementframe and may receive a MAC response frame. The TXOP has a longest timelimit, and when this is ended, a TXOP may be acquired throughre-competition. Correspondingly, in enhanced distributed channel access(EDCA), each access category (AC) may also independently acquire theTXOP and exclusively occupy the channel resource. A node which hasacquired the TXOP is named as a TXOP holder, and a node correspondinglyestablishing a transmission link with the TXOP holder is named as a TXOPresponder.

After the TXOP holder successfully acquires the TXOP, the TXOP holderand the TXOP responder set NAV values for stations under the coverage ofthe TXOP holder and the TXOP responder through exchange of a first pairof MAC frames to forbid the stations to access to the channel resourcewithin a NAV time period, unless a station is required by the TXOPholder to become the TXOP responders, and the station feeds back a MACresponse frame. In the subsequent TXOP time period, a node setting theNAV continues to monitor a MAC frame it received, and if a destinationaddress of the monitored MAC frame does not match with a local address,a local NAV value is updated according to a field value of a time lengthfield in the MAC frame, and if the destination address matches with thelocal address, a NAV value stored locally is not updated. In addition,the NAV value in each node may decrease continuously over time, and whenthe NAV value is 0, a node being set the NAV value may performcompetition for channel access through the physical carrier monitoringmechanism. If the TXOP holder discovers that a transmission sequence isnull (no service data needs to be transmitted) within the TXOP timelimit and it is needed to end the TXOP ahead of time, and the length ofthe remaining time of the current TXOP exceeds the length of a time forretransmitting a CF_End frame, the TXOP holder transmits the CF_Endframe to abandon a right to access to the channel resource, wherein afield value of a time length field in the CF_End frame is 0. The otherstations under the coverage of the TXOP holder monitor the CF_End frame,clear the NAV values stored locally according to the field value of thetime length field and may perform competition for channel access throughthe physical carrier monitoring mechanism.

However, the inventor discovers that, the CF_End frame transmitted bythe TXOP holder only enables the NAV value of a station under thecoverage of the TXOP holder to be updated to 0. A hidden station may notreceive the CF_End frame because it is not under the coverage of theTXOP holder, so the NAV value of the hidden station may not change. Thehidden station may only continue to wait until the local NAV valuedecreases to 0 and may enter a channel access competition state. Thetime of entering the channel access competition state of the hiddenstation is apparently later than that of a node under the coverage ofthe TXOP holder. Therefore, the hidden station may not enter the channelaccess competition state timely according to the situation that the TXOPis ended ahead of time, thus a problem of regional discrimination of astation exists.

SUMMARY

Accordingly, the technical problem to be solved by the present inventionis to provide a method, a device and a system for performing NAV controlon a node and a node, which enable a hidden node to enter a channelaccess competition state timely, thereby solving a problem of regionaldiscrimination of a station.

Therefore, embodiments of the present invention adopt the followingtechnical solutions.

An embodiment of the present invention provides a method for performingNAV control on a node, including:

updating a local NAV value to a preset first value when it is determinedthat a preset first field of a monitored MAC frame carries a firstidentity, wherein the first value is smaller than a current local NAVvalue and the MAC frame of which the preset first field carriers thefirst identity is transmitted by a TXOP responder after receiving a lastMAC frame transmitted by a TXOP holder.

An embodiment of the present invention also provides a method forperforming NAV control on a node, including:

receiving a MAC frame transmitted by a TXOP holder;

transmitting a MAC response frame corresponding to the MAC frame to theTXOP holder when it is determined according to a field value of a presetsecond field in the MAC frame that the MAC frame is a last MAC frametransmitted by the TXOP holder, wherein a preset first field of the MACresponse frame carries a first identity, and the first identity is usedfor instructing a node monitoring the MAC response frame to update alocal NAV value to a first value.

An embodiment of the present invention provides a device for performingNAV control on a node, including:

an updating unit, configured to update a local NAV value to a presetfirst value when it is determined that a preset first field of amonitored MAC frame carries a first identity, wherein the first value issmaller than a current local NAV value and the MAC frame of which thepreset first field carriers the first identity is transmitted by a TXOPresponder after receiving a last MAC frame transmitted by a TXOP holder.

An embodiment of the present invention provides a device for performingNAV control on a node, including:

a first receiving unit, configured to receive a MAC frame transmitted bya TXOP holder;

a first transmitting unit, configured to transmit a MAC response framecorresponding to the MAC frame to the TXOP holder when it is determinedaccording to a field value of a preset second field in the MAC framethat the MAC frame is a last MAC frame transmitted by the TXOP holder,wherein a preset first field of the MAC response frame carries a firstidentity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value to a firstvalue.

An embodiment of the present invention provides a node, including:

an updating unit, configured to update a local NAV value to a presetfirst value when it is determined that a preset first field of amonitored MAC frame carries a first identity, wherein the first value issmaller than a current local NAV value and the MAC frame of which thepreset first field carriers the first identity is transmitted by a TXOPresponder after receiving a last MAC frame transmitted by a TXOP holder.

An embodiment of the present invention provides a system for performingNAV control on a node, including:

a TXOP holder, configured to transmit a last MAC frame to a TXOPresponder, wherein a field value of a preset second field in the lastMAC frame is used for indicating for the TXOP responder that the MACframe is the last MAC frame transmitted by the TXOP holder, and receivea MAC response frame transmitted by the TXOP responder and correspondingto the last MAC frame, wherein a preset first field of the MAC responseframe carries a first identity and the first identity is used forinstructing a node monitoring the MAC response frame to update a localNAV value to a first value;

the TXOP responder, configured to receive a MAC frame transmitted by theTXOP holder and transmit a MAC response frame corresponding to the MACframe to the TXOP holder when it is determined according to a fieldvalue of a preset second field in the MAC frame that the MAC frame is alast MAC frame transmitted by the TXOP holder;

a first node, configured to update a local NAV value to a preset firstvalue when it is determined that a preset first field of a monitored MACframe carries a first identity, wherein the first value is smaller thana current local NAV value.

The technical effects of the above-mentioned technical solutions areanalyzed as follows.

After receiving a last MAC frame transmitted by a TXOP holder, a TXOPresponder transmits a MAC response frame carrying a first identity in apreset first field, and when a node in the coverage of the TXOPresponder monitors the MAC frame, the node updates a local NAV value toa first value. Therefore, even if the TXOP holder abandons a right toaccess to a channel resource ahead of time, a hidden node may update alocal NAV value to the first value according to the MAC response frametransmitted by the TXOP responder and carrying the first identity in thefirst field, so that the time when the hidden node enters a channelaccess competition state is not later than the time when a node underthe coverage of the TXOP holder enters the channel access competitionstate, and all the nodes in the coverage of the TXOP holder and the TXOPresponder may enter the channel access competition state timely, therebysolving a problem that the hidden node is unable to enter the channelaccess competition state timely, namely solving the problem of regionaldiscrimination of the node.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is schematic diagram of a structure of a WLAN in the prior art;

FIG. 2 is an example diagram of a hidden node problem in the prior art;

FIG. 3 is a schematic flowchart of a first method for performing NAVcontrol on a node in an embodiment of the present invention;

FIG. 4 is a schematic flowchart of a second method for performing NAVcontrol on a node in an embodiment of the present invention;

FIG. 5 is a schematic flowchart of a third method for performing NAVcontrol on a node in an embodiment of the present invention;

FIG. 6 is a schematic flowchart of a method for performing MAC frameexchange in a TXOP by a TXOP holder and a TXOP responder in anembodiment of the present invention;

FIG. 7 is a schematic flowchart of a fourth method for performing NAVcontrol on a node in an embodiment of the present invention;

FIG. 8 is a schematic flowchart of a fifth method for performing NAVcontrol on a node in an embodiment of the present invention;

FIG. 9 is a schematic diagram of a structure of a first device forperforming NAV control on a node in an embodiment of the presentinvention;

FIG. 10 is a schematic diagram of a structure of a second device forperforming NAV control on a node in an embodiment of the presentinvention;

FIG. 11 is a schematic diagram of a structure of a third device forperforming NAV control on a node in an embodiment of the presentinvention; and

FIG. 12 is a schematic diagram of a structure of a system for performingNAV control on a node in an embodiment of the present invention.

DETAILED DESCRIPTION

Implementation of a method, a device and a system for performing networkallocation vector (NAV) control on a node and a node in the embodimentsof the present invention is described below in details, in combinationwith the accompanying drawings.

FIG. 3 is a schematic flowchart of a method for performing NAV controlon a node in an embodiment of the present invention. The method may beapplied to a node in the coverage of a TXOP responder in a TXOP, andpreferably, may be applied to a hidden node in the coverage of the TXOPresponder in the TXOP but not in the coverage of a TXOP holder. As shownin FIG. 3, the method includes:

step 301: updating a local NAV value to a preset first value when it isdetermined that a preset first field of a monitored MAC frame carries afirst identity, wherein the first value is smaller than a current localNAV value and the MAC frame of which the preset first field carriers thefirst identity is transmitted by a TXOP responder after receiving a lastMAC frame transmitted by a TXOP holder.

The first value may be preset in each node, so that the updating processis performed when the MAC frame carrying the first identity in thepreset first field is monitored.

In addition, the first value may be 0.

Preferably, the first value may be set as the sum of a time of a shortinter-frame space (SIFS) and a time of transmission of a CF_End frame.In this case, after the hidden node updates the NAV value to the firstvalue, the NAV value continues decreasing, During the time that the NAVvalue of the hidden node decreases from the first value to 0, the TXOPholder also receives the MAC frame carrying the first identity in thepreset first field, and then transmits a CF_End frame to realizeclearing a NAV value of a node under the coverage of the TXOP holder,The NAV values of the hidden node and the node under the coverage of theTXOP holder are updated to 0 at the same time, and the two nodes performcompetition for channel access together.

Preferably, the first field may be a time length field, and the firstidentity may be 0.

Here, the current local NAV value is a local NAV value before theupdating of the NAV value, namely a local NAV value when the MAC frameis monitored.

In the method shown in FIG. 3, after receiving the last MAC frametransmitted by the TXOP holder, the TXOP responder transmits the MACframe carrying the first identity in the preset first field, and whenthe node in the coverage of the TXOP responder monitors the MAC frame,the node updates the local NAV value to the first value. Therefore, evenif the TXOP holder abandons a right to access to a channel resourceahead of time, all the nodes in the coverage of the TXOP holder and theTXOP responder may enter a channel access competition state timely,thereby solving a problem that the hidden node is unable to enter thechannel access competition state timely, namely solving the problem ofregional discrimination of the node.

FIG. 4 shows another method for performing NAV control on a node in anembodiment of the present invention. The method may be applied to a TXOPresponder in a TXOP. As shown in FIG. 4, the method includes:

step 401: receiving a MAC frame transmitted by a TXOP holder; step 402:transmitting a MAC response frame corresponding to the MAC frame to theTXOP holder when it is determined according to a field value of a presetsecond field in the MAC frame that the MAC frame is a last MAC frametransmitted by the TXOP holder, wherein a preset first field of the MACresponse frame carries a first identity, and the first identity is usedfor instructing a node monitoring the MAC response frame to update alocal NAV value to a first value.

In the method shown in FIG. 4, when a TXOP responder receives the MACframe transmitted by the TXOP holder and determines the MAC frame is thelast MAC frame transmitted by the TXOP holder, the TXOP respondertransmits the MAC response frame carrying the first identity in thepreset first field to the TXOP holder, wherein the first identity isused for instructing the node monitoring the MAC response frame toupdate the local NAV value to the first value. Therefore, in the TXOP,if the TXOP holder releases or abandons a right to access to a channelresource ahead of time, a hidden node may update the local NAV value tothe first value when monitoring the MAC response frame, transmitted bythe TXOP responder, of the last MAC frame, so as to enter a channelaccess competition state not later than other nodes under the coverageof the TXOP holder, thereby solving the problem that the hidden node isunable to enter the channel access competition state timely, namelysolving the problem of regional discrimination of the node.

FIG. 5 is a schematic flowchart of a third method for performing NAVcontrol on a node in an embodiment of the present invention. The methodmay be applied to a TXOP holder in a TXOP. As shown in FIG. 5, themethod includes:

step 501: transmitting a last MAC frame to a TXOP responder, wherein afield value of a preset second field in the last MAC frame is used forindicating for the TXOP responder that the MAC frame is the last MACframe transmitted to the TXOP responder by the TXOP holder; step 502:receiving a MAC response frame transmitted by the TXOP responder andcorresponding to the last MAC frame, wherein a preset first field of theMAC response frame carries a first identity, and the first identity isused for instructing a node monitoring the MAC response frame to updatea local NAV value to a first value.

In the method shown in FIG. 5, after transmitting the last MAC frame tothe TXOP responder, the TXOP holder receives the MAC response framecarrying the first identity in the preset first field transmitted by theTXOP responder, so as to perform transmission of the MAC frame throughcooperation with the TXOP responder, enabling a hidden node under thecoverage of the TXOP responder to enter the channel access competitionstate timely, and solving the problem of regional discrimination of thenode.

An exchange process between a TXOP holder and a TXOP responder in a TXOPis described below through embodiments, so as to further illustrate theimplementation of the method for performing NAV control on a node in theembodiments of the present invention in details. Specifically, theprocess is performed after a certain node wins a channel resource anddetermines that the current TXOP is acquired through successful exchangeof a first frame. As shown in FIG. 6, the method includes:

Step 601: a TXOP holder transmits a MAC frame to a TXOP responder.

A MAC frame is a field set occurring in a given sequence contained in aMAC layer, wherein each MAC frame includes a MAC frame header, avariable length frame body including information of a specific subframetype or subtype and a frame check sequence. The MAC frame may be a dataframe, a management frame, a control frame or the like.

Not all fields occur in a transmitted MAC frame exchanged by the TXOPholder and the TXOP responder in the MAC layer, meanwhile, values of asame field in different conditions may be different.

For example, a MAC frame may include a time length field, a more datafield in a frame control field, an acknowledgment policy field in a QoScontrol field and the like, wherein the more data field is used forindicating whether the TXOP holder has a subsequent frame to transmit tothe TXOP responder after the current transmitted MAC frame, theacknowledgment policy field is used for indicating whether an immediatefeedback is required after the TXOP responder receives the currenttransmitted MAC frame, and the time length field is used for anon-destination node monitoring the MAC frame to update a local NAVvalue according to a field value of the time length field.

A time length value of a MAC frame in a TXOP may be the remaining timelength t_(TXOP) ^(r) (t_(TXOP) ^(r)>0) of the TXOP at the moment whentransmission of the MAC frame is ended.

Step 602: the TXOP responder receives the MAC frame, determines whetherthe TXOP holder has a subsequent frame to transmit, and determineswhether an immediate feedback to the received MAC frame is required; ifboth are yes, step 603 is performed; if it is determined that the TXOPholder does not have a subsequent frame to transmit and an immediatefeedback to the received MAC frame is required, step 604 is performed;otherwise, step 606 is performed.

Determining whether the TXOP holder has a subsequent frame to transmitmay be performed according to a field value of a certain preset secondfield such as the more data field in the MAC frame. For example, when avalue of the more data field is preset as 1, it is indicated that theTXOP holder has a subsequent frame to transmit to the TXOP responder,and when the value is 0, it is indicated that the TXOP holder does nothave a subsequent frame to transmit to the TXOP responder. The methodfor determining whether the TXOP holder has a subsequent frame totransmit to the TXOP responder in this step may include: analyzing thefield value of the more data field of the received MAC frame; when thefield value is 1, determining that the TXOP holder has a subsequentframe to transmit to the TXOP responder; otherwise, determining that theTXOP holder does not has a subsequent frame to transmit to the TXOPresponder.

Similarly to the method for determining whether the TXOP holder has asubsequent frame to transmit to the TXOP responder, whether a immediatefeedback to the received MAC frame is required may also be determinedaccording to a field value of the acknowledgment policy field in the MACframe, and will not be described redundantly herein.

Step 603: the TXOP responder transmits a MAC response frame to the TXOPholder, wherein a value of a time length field in the MAC response framemay be the remaining time length t_(TXOP) ^(rr)(t_(TXOP) ^(rr)) of theTXOP at the moment when transmission of the MAC response frame is ended.

Here, the MAC response frame may also be a MAC frame, which may be anACK frame, a BA frame or a MAC frame of other types, and the so-calledMAC response frame is merely to distinguish from the MAC frametransmitted from the TXOP holder to the TXOP responder.

After this step is performed and the TXOP holder receives the MACresponse frame transmitted by the TXOP responder, the method switchesback to the step 601, and the TXOP holder transmits a next MAC frame tothe TXOP responder.

Step 604: the TXOP responder transmits a MAC response frame to the TXOPholder, wherein a preset first field in the MAC response frame carries afirst identity, and the first identity is used for instructing a nodemonitoring the response frame to update a local NAV value to a firstvalue; and step 605 is performed.

Generally, the first field may be a time length field, and the firstidentity may be 0 serving as the first identity, which is not limitedhere, as long as another node monitoring the MAC frame may clear thelocal NAV value according to the first identity in the first field.

After this step is performed and the TXOP holder receives the MACresponse frame transmitted by the TXOP responder, the TXOP holder hasalready learnt that release of a right to access to a channel resourceis completed according to the MAC response frame, and step 605 isperformed.

Step 605: the TXOP holder transmits a CF_End frame to instruct a node inthe coverage of itself to clear a local NAV value, and ends servicetransmission to the TXOP responder.

According to the CF_End frame transmitted by the TXOP holder, a node notbeing the TXOP responder under the coverage of the TXOP holder clearsthe local NAV value so as to enter a channel access competition state,and service transmission from the TXOP holder to the TXOP responder isended.

Step 606: if it is determined that the TXOP holder has a subsequentframe to transmit and an immediate feedback to the received MAC frame isnot required, the TXOP responder analyzes the MAC frame and does notfeed back a MAC response frame; at this moment, the method switches backto the step 601, and the TXOP holder transmits a next MAC frame to theTXOP responder; if it is determined that the TXOP holder does not have asubsequent frame to transmit and an immediate feedback to the receivedMAC frame is not required, the TXOP responder does not perform afeedback of a MAC response frame, and the TXOP holder ends servicetransmission to the TXOP responder in the current TXOP.

In the exchange process between the TXOP holder and the TXOP respondershown in the above FIG. 6, other nodes under the coverage of the TXOPholder and the TXOP responder continuously monitor a MAC frame all thetime. A node under the coverage of the TXOP holder may monitor a MACframe transmitted from the TXOP holder to the TXOP responder, and a nodeunder the coverage of the TXOP responder may monitor a MAC responseframe fed back from the TXOP responder to the TXOP holder.

In a monitoring process, a node may update a local NAV value accordingto a field value of a time length field of each monitored MAC frame. Inthis case, as shown in FIG. 7, a NAV control process of the other nodesunder the coverage of the TXOP holder and the TXOP responder mayinclude:

Step 701: monitoring a MAC frame.

Step 702: determining whether a preset first field of a monitored MACframe carries a first identity; if yes, performing step 703; if not,performing step 704.

A MAC frame carrying a first identity in a preset first field is a MACresponse frame transmitted by a TXOP responder to a TXOP holder afterthe TXOP responder receives a last MAC frame transmitted by the TXOPholder.

Preferably, the first field is a time length field, and the firstidentity may be 0.

Step 703: updating a local NAV value to a first value to enter a channelaccess competition state.

Step 704: updating a local NAV value according to a field value of atime length field of the MAC frame.

The updating the local NAV value according to the field value of thetime length field of the MAC frame may include:

comparing, by a node, the field value of the time length field of themonitored MAC frame with the local NAV value, and taking the bigger oneof the two values to update the local NAV, namely, if the field value ofthe time length field is bigger than the local NAV value, updating thelocal NAV value to the field value of the time length field, and if thefield value of the time length field is not bigger than the local NAVvalue, not updating the local NAV value.

In the method shown in FIG. 7, a node only under the coverage of theTXOP holder may only monitor a MAC frame transmitted from the TXOPholder to the TXOP responder, so the local NAV is updated according tothe MAC frame; a node only under the coverage of the TXOP responder mayonly monitor a MAC response frame transmitted from the TXOP responder tothe TXOP holder, so the local NAV is updated according to the MACresponse frame; and a node under the coverage of both the TXOP holderand the TXOP responder may monitor a MAC frame transmitted by the TXOPholder and a MAC response frame transmitted by the TXOP responder, sothe local NAV is updated when each of the two MAC frames is monitored,thus when the TXOP holder and the TXOP responder perform a round ofexchange of the MAC frames, the node needs to update the NAV valuetwice.

Preferably, in order to reduce the times for updating the NAV value bythe node under the coverage of both the TXOP holder and the TXOPresponder and to reduce data processing pressure of the node under thecoverage of both the TXOP holder and the TXOP responder, the NAV valueupdating of the node under the coverage of both the TXOP holder and theTXOP responder may be only controlled by the TXOP holder. In this case,as shown in FIG. 8, a processing flow of the node includes:

Step 801: when a local NAV value of a node is in a zero value state anda first MAC frame is monitored, determining whether the monitored MACframe is the first MAC frame transmitted by a TXOP holder; if yes,performing step 802; if not, performing step 805.

When the local NAV value of the node is in the zero value state, it isindicated that the node may compete for channel access through aphysical carrier monitoring mechanism. If a MAC frame is monitoredbefore the node does not acquire the channel access, it is indicatedthat a channel has already been occupied by another node; if it islearnt through analysis that the MAC frame is an RTS frame, it isindicated that another node wins a TXOP, the MAC frame is the first MACframe transmitted by the TXOP holder, and the node is under the coverageof the TXOP holder; otherwise, the node is under the coverage of a TXOPresponder.

Here, a first frame transmitted by the TXOP holder is generally an RTSframe, so the determining in this step may be realized by determiningwhether the monitored MAC frame is the RTS frame.

Step 802: storing an address of the TXOP holder, carried in the MACframe, and updating a local NAV value according to a field value of atime length field in the MAC frame; and performing step 803.

The address of the TXOP holder is a transmitting node address carried inthe MAC frame.

Implementation of the updating the local NAV value in this step may bereferred to the description in the step 704, and will not be describedredundantly herein.

Step 803, continuing to monitor a MAC frame, when the MAC frame ismonitored, determining whether the transmitting node address carried inthe MAC frame is consistent with the address of the TXOP holder; if yes,performing step 804; if no, continuing to monitor a MAC frame.

Step 804, updating the local NAV value according to the field value ofthe time length field in the monitored MAC frame; and switching back tostep 803 to continue to monitor a MAC frame, until the local NAV valueis clear, and entering a channel access competition state.

Specific updating method may be referred to the related description inthe step 704, and will not be described redundantly herein.

Through cyclic processing of the step 802 to the step 804, the nodeunder the coverage of both the TXOP holder and the TXOP responder mayupdate the local NAV value according to the MAC frame transmitted by theTXOP holder rather than the MAC frame transmitted by the TXOP responder,thereby reducing the data processing pressure of the node under thecoverage of both the TXOP holder and the TXOP responder.

Step 805, determining whether a preset first field of the monitored MACframe carries a first identity; if not, performing step 806; if yes,performing step 807.

Step 806: updating the local NAV value according to the field value ofthe time length field in the MAC frame.

Step 807: updating the local NAV value to a first value.

When the first value is 0, a node monitoring the MAC frame carrying thefirst identity in the preset first field updates the local NAV value to0, and enters the channel access competition state.

When the first value is the sum of a time of a short inter-frame spaceand a time of transmission of a CF_End frame, the node monitoring theMAC frame carrying the first identity in the preset first field maycontinue decreasing the NAV value, until the NAV value is decreased to0, and the node enters the channel access competition state.

The process that the hidden node only under the coverage of the TXOPresponder performs local NAV value control is realized through the step805 to the step 807, and the hidden node clears the local NAV value bymonitoring the MAC frame carrying the first identity in the preset firstfield transmitted by the TXOP responder and enters the channel accesscompetition state.

In the embodiments shown in FIG. 6 to FIG. 8, a transmission mode thatthe TXOP holder and the TXOP responder perform service transmissionone-to-one is taken as an example, In actual application, the methodsfor performing NAV control on a node in the embodiments of the presentinvention may also be applied to a service transmission mode ofperforming transmission by a TXOP holder to multiple TXOP responders atdivided times, or performing transmission by a TXOP holder to multipleTXOP responders at the same time. When the TXOP holder performstransmission to the multiple TXOP responders at the same time or atdivided times, the transmission process may be decomposed into multipletransmission processes that the TXOP holder and the TXOP responderperform service transmission one to one. Each decomposed transmissionprocess that the TXOP holder and the TXOP responder perform servicetransmission one to one may use the methods for performing node NAVcontrol as shown in FIG. 6 to FIG. 8 of the present inventioncorrespondingly, and will not be described redundantly herein.

Corresponding to the above-mentioned methods, the embodiments of thepresent invention also provide devices for performing NAV control on anode.

FIG. 9 is a schematic diagram of a structure of a first device forperforming NAV control on a node in an embodiment of the presentinvention. The device may be arranged in a node in the coverage of aTXOP responder in a TXOP, and preferably, may be arranged in a hiddennode in the coverage of the TXOP responder rather than in the coverageof a TXOP holder in the TXOP. The device includes:

an updating unit 910, configured to update a local NAV value to a presetfirst value when it is determined that a preset first field of amonitored MAC frame carries a first identity, wherein the first value issmaller than a current local NAV value and the MAC frame of which thepreset first field carriers the first identity is transmitted by a TXOPresponder after receiving a last MAC frame transmitted by a TXOP holder.

Preferably, as shown in FIG. 9, the device may further include: adetermining unit, configured to determine, when the local NAV value isin a zero value state and a first MAC frame is monitored, whether themonitored MAC frame is the first MAC frame transmitted by the TXOPholder; a first processing unit, configured to store an address of theTXOP holder carried in the MAC frame when the monitored MAC frame is thefirst MAC frame transmitted by the TXOP holder, update the local NAVvalue according to a field value of a time length field in the MACframe, and update the local NAV value according to a field value of atime length field in a monitored MAC frame when the MAC frame ismonitored subsequently and it is determined that an address of atransmitting node carried in the MAC frame is consistent with theaddress of the TXOP holder; and a second processing unit, configured todetermine whether the preset first field of the monitored MAC framecarries the first identity when the monitored MAC frame is not the firstMAC frame transmitted by the TXOP holder, and update the local NAV valueaccording to a field value of a time length field in the MAC frame ifthe first identity is not carried, wherein the updating operation isperformed by the updating unit if the first identity is carried.

Preferably, the determining unit realizes determining whether themonitored MAC frame is the first MAC frame transmitted by the TXOPholder by determining whether the monitored MAC frame is an RTS frame.

Preferably, the second processing unit may realize updating the localNAV value according to a field value of a time length field in the MACframe in the following modes:

updating the local NAV value to the field value of the time length fieldwhen it is determined that the field value of the time length field inthe MAC frame is bigger than the local NAV value; and not updating thelocal NAV value when it is determined that the field value of the timelength field in the MAC frame is not bigger than the local NAV value.

FIG. 10 is a schematic diagram of a structure of a second device forperforming NAV control on a node in an embodiment of the presentinvention. The device may be arranged in a TXOP responder. The deviceincludes:

a first receiving unit 1010, configured to receive a MAC frametransmitted by a TXOP holder;

a first transmitting unit 1020, configured to transmit a MAC responseframe corresponding to the MAC frame to the TXOP holder when it isdetermined according to a field value of a preset second field in theMAC frame that the MAC frame is a last MAC frame transmitted by the TXOPholder, wherein a preset first field of the MAC response frame carries afirst identity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value to a firstvalue.

FIG. 11 is a schematic diagram of a structure of a third device forperforming NAV control on a node in an embodiment of the presentinvention. The device may be arranged in a TXOP holder. The deviceincludes:

a second transmitting unit 1110, configured to transmit a last MAC frameto a TXOP responder, wherein a field value of a preset second field inthe last MAC frame is used for indicating for the TXOP responder thatthe MAC frame is the last MAC frame transmitted by a TXOP holder;

a second receiving unit 1120, configured to receive a MAC response frametransmitted by the TXOP responder and corresponding to the last MACframe, wherein a preset first field of the MAC response frame carries afirst identity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value to a firstvalue.

In addition, an embodiment of the present invention also provides anode, including:

an updating unit, configured to update a local NAV value to a presetfirst value when it is determined that a preset first field of amonitored MAC frame carries a first identity, wherein the first value issmaller than a current local NAV value and the MAC frame of which thepreset first field carriers the first identity is transmitted by a TXOPresponder after receiving a last MAC frame transmitted by a TXOP holder.

In addition, the node may further include:

a first receiving unit, configured to receive a MAC frame transmitted bya TXOP holder;

a first transmitting unit, configured to transmit a MAC response framecorresponding to the MAC frame to the TXOP holder when it is determinedaccording to a field value of a preset second field in the MAC framethat the MAC frame is a last MAC frame transmitted by the TXOP holder,wherein a preset first field of the MAC response frame carries a firstidentity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value to a firstvalue.

In addition, the node may further include:

a second transmitting unit, configured to transmit a last MAC frame to aTXOP responder, wherein a field value of a preset second field in thelast MAC frame is used for indicating for the TXOP responder that theMAC frame is the last MAC frame transmitted by a TXOP holder; a secondreceiving unit, configured to receive a MAC response frame transmittedby the TXOP responder and corresponding to the last MAC frame, wherein apreset first field of the MAC response frame carries a first identity,and the first identity is used for instructing a node monitoring the MACresponse frame to update a local NAV value to a first value

Through the updating unit, the node may serve as a node which is underthe coverage of the TXOP holder or the TXOP and is not the TXOP holderor the TXOP responder node in the TXOP; through the first receiving unitand the first transmitting unit, the node may serve as the TXOPresponder in the TXOP to cooperate with the TXOP holder to performservice transmission; and through the second transmitting unit and thesecond receiving unit, the node may serve as the TXOP holder in the TXOPto cooperate with the TXOP responder to perform service transmission.

In addition, an embodiment of the present invention also provides asystem for performing NAV control on a node, as shown in FIG. 12,including:

a TXOP holder 1210, configured to transmit a last MAC frame to a TXOPresponder, wherein a field value of a preset second field in the lastMAC frame is used for indicating for the TXOP responder that the MACframe is the last MAC frame transmitted by the TXOP holder, and receivea MAC response frame transmitted by the TXOP responder and correspondingto the last MAC frame, wherein a preset first field of the MAC responseframe carries a first identity and the first identity is used forinstructing a node monitoring the MAC response frame to update a localNAV value to a first value;

the TXOP responder 1220, configured to receive a MAC frame transmittedby the TXOP holder and transmit a MAC response frame corresponding tothe MAC frame to the TXOP holder when it is determined according to afield value of a preset second field in the MAC frame that the MAC frameis a last MAC frame transmitted by the TXOP holder; a first node 1230,configured to update a local NAV value to a preset first value when itis determined that a preset first field of a monitored MAC frame carriesa first identity, wherein the first value is smaller than a currentlocal NAV value.

Preferably, in the above-mentioned devices, node and system, the firstvalue may be 0 or the sum of a time of a short inter-frame space and atime of transmission of a CF_End frame.

The preset second field may be a more data field, the preset first fieldmay be a time length field, and the first identity may be 0.

In the above-mentioned devices, node and system, when the TXOP responderreceives the last MAC frame transmitted by the TXOP holder, the TXOPresponder transmits the MAC response frame carrying the first identityin the preset first field, and when the node in the coverage of the TXOPresponder monitors the MAC frame, the node updates the local NAV valueto the first value. Therefore, even if the TXOP holder abandons theright to access to the channel resource ahead of time, the hidden nodemay update the local NAV value to the first value according to the MACresponse frame transmitted by the TXOP responder and carrying the firstidentity in the first field, so that the time when the hidden nodeenters the channel access competition state is not later than the timewhen the node under the coverage of the TXOP holder enters the channelaccess competition state, and all the nodes in the coverage of the TXOPholder and the TXOP responder may enter the channel access competitionstate timely, thereby solving the problem that the hidden node is unableto enter the channel access competition state timely, namely solving theproblem of regional discrimination of the node.

It should be appreciated for those of ordinary skill in the art that theprocesses of the methods of the above-mentioned embodiments may beimplemented with a computer program instructing corresponding hardware,the program may be stored in a readable storage medium, and thecorresponding steps in the above-mentioned methods are performed whenthe program is executed. The storage medium may be a ROM/RAM, a magneticdisk, an optical disk, or the like.

The foregoing descriptions are merely preferred implementation mannersof the present invention. It should be noted that, for those of ordinaryskill in the art, a plurality of improvements and modifications may bemade without departing from the principle of the present invention.These improvements and modifications should be included in theprotection scope of the present invention.

What is claimed is:
 1. A method for performing network allocation vector(NAV) control on a node, the method comprising: receiving, by a transmitopportunity (TXOP) responder, a media access control (MAC) frametransmitted by a TXOP holder; and transmitting, by the TXOP responder, aMAC response frame corresponding to the MAC frame to the TXOP holderwhen the MAC frame is a last MAC frame transmitted by the TXOP holder,wherein a preset first field of the MAC response frame carries a firstidentity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value of thenode to zero.
 2. The method according to claim 1, wherein the node is ahidden node which is in the coverage of the TXOP responder but not inthe coverage of the TXOP holder.
 3. The method according to claim 1,wherein the preset first field is a time length field.
 4. The methodaccording to claim 1, further comprising: determining, by the TXOPresponder, the MAC frame is a last MAC frame transmitted by the TXOPholder, according to a preset second field of the MAC frame.
 5. Themethod according to claim 4, wherein determining, by the TXOP responder,the MAC frame is a last MAC frame transmitted by the TXOP holder,according to a preset second field of the MAC frame, comprises:determining, by the TXOP responder, the MAC frame is the last MAC frametransmitted by the TXOP holder, when a value of a more data field is 0,wherein the preset second field is the more data field.
 6. A device of atransmit opportunity (TXOP) responder for performing network allocationvector (NAV) control on a node, comprising: a transceiver, configured toreceive a media access control (MAC) frame transmitted by a TXOP holder;and a processor, configured to control the transceiver to transmit a MACresponse frame corresponding to the MAC frame to the TXOP holder whenthe MAC frame is a last MAC frame transmitted by the TXOP holder,wherein a preset first field of the MAC response frame carries a firstidentity, and the first identity is used for instructing a nodemonitoring the MAC response frame to update a local NAV value of thenode to zero.
 7. The device according to claim 6, wherein the node is ahidden node which is in the coverage of the TXOP responder but not inthe coverage of the TXOP holder.
 8. The device according to claim 6,wherein the preset first field is a time length field.
 9. The deviceaccording to claim 6, wherein the processor is further configured to:determine the MAC frame is a last MAC frame transmitted by the TXOPholder according to a preset second field of the MAC frame.
 10. Thedevice according to claim 9, wherein the processor is further configuredto: determine the MAC frame is the last MAC frame transmitted by theTXOP holder, when a value of a more data field is 0, wherein the presetsecond field is the more data field.